This invention relates in general to gas turbine engines and in particular to a combined temperature and pressure probe for intake air to a gas turbine engine.
Gas turbine engines, or jet engines, have been widely adopted to power aircraft, where their simplicity and operating efficiency provides high reliability with low operating costs. A sectional view of a gas turbine engine is shown generally at 10 in FIG. 1. The engine 10 includes three primary parts. A compressor 12 located to the left of FIG. 1 is disposed within an engine intake housing 13. The compressor 12 consists of a plurality of fan blades 14 attached in rows to a cone-shaped cylinder 16. To the right of the compressor 12 is the second primary part of the engine, which is a combustion chamber 18. The combustion chamber 18 includes a perforated flame holder 20 that has a generally cylindrical shape. A plurality of fuel injectors are 22 positioned at the left end of the flame holder 20. To the right of the gas turbine engine 10 is a multi-bladed turbine 24 that forms the third primary part of the engine. The turbine 24 is connected by a rotatable shaft 26 that passes through the combustion chamber 18 to the compressor 12. Thus, rotation of the turbine 24 also rotates the compressor 12.
During operation of the engine 10, the compressor 12 spins and draws air into the engine, as illustrated by the arrow at the left of FIG. 1. The compressor 12 compresses the air and then forces the air into the combustion chamber 18 through the perforations in the flame holder 20. Fuel is injected into the combustion chamber 18 through the fuel injectors 22 and ignited. The resulting hot gases are expelled to the right of FIG. 1, where they drive the turbine blades and thereby spin the turbine 24, which, in turn spins the compressor 12. The hot gases are then exhausted from the engine 10, as illustrated by the arrow at the right of FIG. 1.
Successful operation of the engine 10 requires that the flow of fuel into the combustion chamber 18 be carefully controlled. The fuel flow must be coordinated with the temperature and pressure of the air entering the engine intake housing 13. Typically, a temperature sensor 30 and a separate pressure probe 32 are mounted upon the engine intake housing 13 and provide air temperature and pressure data to an engine controller 34. As best seen in FIG. 2, the pressure probe 32 usually consists of a tube 34 having an open end 36 that extends through a first sensor opening 37 in the housing. The tube 34 is bent 90 degrees such that the open end 36 of the tube 34 receives a portion of the incoming air stream. A flexible hollow hose 38 is attached to the portion of the tube 34 that extends outside of the intake housing 13. The hose 38 passes through an aperture 40 formed in a side of an engine controller housing 42 and is attached to a pressure transducer 44. Thus, the pressure of the intake air is directly applied through the hose 38 to the pressure transducer 44. The pressure transducer 44, which generates an electrical voltage that is proportional to the air pressure within the tube 34 and hose 38, is mounted upon a Printed Circuit Board (PCB) 46 that is disposed within the controller housing 42.
Similarly, the temperature sensor 30 extends through a second sensor opening 47 in the intake housing 13 and is operative to generate a voltage that is proportional to the air temperature within the intake housing 13. The air temperature voltage is transferred over a wiring harness 48 that is attached to the temperature sensor 30 and extends through the side of the controller housing 42. The harness wires are electrically connected to conductive traces disposed upon the surface of the PCB 46. The PCB 46 also carries electronic components (not shown) that are responsive to intake air temperature and pressure for controlling the operation of the gas turbine engine 10. Typically, the temperature sensor wiring harness 48 terminates at an electrical connector (not shown) that is mounted upon the controller housing 42. The electrical connector allows removal of the engine controller for servicing without disturbing the temperature sensor 30.
As described above, it is known to mount separate temperature and pressure sensors upon the intake housing of a gas turbine engine. The pressure sensor is connected by a tube to a pressure transducer that is mounted within an engine controller. The engine controller may be mounted upon the engine or located remotely from the engine. Regardless of the engine controller location, an external wiring harness and associated electrical connector are required to connect the temperature sensor to the engine controller. The wiring harness would typically require electrical shielding. Additionally, a flexible pressure tube is needed to connect the pressure sensor to the engine controller. The wiring harness, electrical connector and pressure tube add weight and cost to the engine while reducing operational reliability. Additionally, two apertures are required in the engine intake housing for mounting the sensors. Accordingly, it would be desirable to simplify the mounting of the temperature and pressure sensors.